This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We investigated the transplacental transfer of CCR5 inhibitors by administering a single dose to pregnant macaques shortly before caesarean section with collection of blood samples of the mother and the newborn. This study will determine the feasibility of CCR5 inhibitors in preventing maternal to infant SIV transmission.